Method of treating finely divided material with a gas

ABSTRACT

&lt;PICT:0916482/III/1&gt; In a continuous method for contacting finely divided particles, e.g. starch, with a gas, e.g. anhydrous hydrogen chloride, a stream of the particles is conveyed through a confined contact space containing the gas and having an inlet and outlet arranged so that they are continuously filled with the particles to prevent escape of the gas.  Particles are fed from a belt 41 (Fig. 1) to a conveyer 10 having a floor 11 and sides 12, which is mounted on a carrier 13 vibrated by an eccentric 19, carrier 13 being supported on flexible struts 28.  The vibrations cause the particles M to flow from right to left, passing through a chamber 32 filled with gas supplied by diffuser 39.  The conveyer floor 11 has V-shaped transverse depressions 35 and 351 below end walls 34 and 341 forming an inlet 36 and an outlet 37.  The particles flow down into and up out of depressions 35 and 351 filling inlet 36 and outlet 37.  Dust formation at openings 36 and 37 is eliminated by flanges 38 and 381. The floor 11 has transverse protuberances 27 which mix the stream of particles to ensure uniform contact with the gas.  Carrier 13 is in the form of a channel and conducts material discharged from conveyer 10.ALSO:In a continuous method for contacting finely divided particles of starch with anhydrous hydrogen chloride, a stream of the particles is conveyed through a confined contact space containing the gas and having an inlet and outlet &lt;PICT:0916482/IV(a)/1&gt; arranged so that they are continuously filled with the particles to prevent escape of the gas.  Particles are fed from a belt 41 (Fig. 1) to a conveyer 10 having a floor 11 and sides 12, which is mounted on a carrier 13 vibrated by an eccentric 19, carrier 13 being supported on flexible struts 28.  The vibrations cause the particles M to flow from right to left, passing through a chamber 32 filled with gas supplied by diffuser 39.  The conveyer floor 11 has V-shaped transverse depressions 35 and 351 below end walls 34 and 341 forming an inlet 36 and an outlet 37.  The particles flow down into and up out of depressions 35 and 351 filling inlet 36 and outlet 37.  Dust formation at openings 36 and 37 is eliminated by flanges 38 and 381. The floor 11 has transverse protuberances 27 which mix the stream of particles to ensure uniform contact with the gas.  Carrier 13 is in the form of a channel and conducts material discharged from conveyer 10.

Dec. 17, 1963 R. L. oPlLA METHOD oF TREATTNG FTNELY DTVIDED MATERIAL WITH A GAs Filed Sept. 30, 1959 www, Mw A- T. @A

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g4 A @w N @A 7A XV@ m United States Patent O 3,114,655 MEBHUD @F TREA'HN'G FINELY DIVIED MATERLAL WITH A GAS Robert L. pila, Westchester, lil., assigner to Corn Products Company, New York, FLY., a corporation of Delaware Filed Sept. 30, 1959, Ser. No. 843,5@ 7 Claims. (Si. 121-33) This invention relates to a method for treating finely divided granular material with a gas, and is particularly concerned with the continuous treatment of such materials with gases which, because of their corrosive or injurious nature, or for reasons of economy, should be confined to the treating zone and not permitted to escape into the surrounding atmosphere. More specifically, the invention is concerned with a novel method for continuously modifying starch by treatment with hydrogen chloride gas.

I employ the terms granular and pulverulent as indicating material in the form of discrete particles, which particles in the dry state are capable of relatively free movement with respect to each other upon being subjected to vibration, i.e., capable of being iiuidized. The term dry as applied to the material operated upon indicates substantial freedom from adherent lms of moisture which would interfere with said free movement.

The acidification of starch for subsequent use in dextrinization is a familiar procedure, and it is well known that the variability of the acid-inactivation power of starch is an important factor which must be considered if a uniform nal product is desired. Suitable changes in acid concentration can of course be made to compensate for a change in acid-inactivation power of starch as soon as such change in acid-inactivation power is detected. In a continuous acidification process the detection of any change in acid-inactivation power of starch can be accomplished after the treatment of a much smaller volume of starch than is possible in a batch process of commercial proportions, because of the relatively small inventory of iii-process starch required by the continuous process as compared to the batch process. This advantage of a continuous starch acidcation process has been recognized in the art, but attempts in the past to develop a continuous process have been hampered by the diiiiculty inherent in effectively sealing the reaction chamber against the escape of corrosive acid fumes as the starch being treated is conveyed through the chamber. As a consequence, starch acidification processes commonly used in the industry have been batch processes which permit the reaction chamber to be tightly closed throughout the reaction period.

it is a broad object of the invention to provide a method for continuously treating a finely divided material with a gas, wherein the material is conveyed through a confined zone containing the treating gas, and wherein packing glands or like sealing means are not required to prevent the escape of the gas from the treating Zone.

A further object of my invention is the provision in a device for contacting a dry finely divided material in granular or pulverulent form with a reactive gas, of a method of moving the dry material through a closed chamber in the form of a thin fluidized stream, the material itself passing through a trap and serving as a gas seal.

A further object of my invention is a method of treating a dry finely divided material with a reactive gas which consists in producing a iiuidized stream of the dry material and causing it to flow into the chamber through an inlet gravity trap; then through the chamber while exposed to the gas, and then out through an outlet gravity trap to the exterior of the chamber.

Another object of the invention is to provide a method lldh Patented Dem ll, i953 ice of contacting a dry iinely divided material such as a starch whether modiiied, or unmodified, with a reactive gas while the dry material is in fluidized form induced by physical vibration.

Other objects and advantages of the invention will in part appear from the following description thereof, and in part will be apparent to those skilled in the art to which the invention pertains.

In general, the apparatus of the invention comprises a trough-shaped vibratory conveyor which is covered over a portion of its length thus providing a tunnel portion or chamber for coniining the treating gas. The tunnel portion or chamber has end walls depending from the top wall and terminating above the floor of the conveyor, forming openings providing ingress and egress to and from the chamber for the finely divided material transported by the conveyor. The conveyor is oscillated longitudinally and is preferably provided within the chamber with transverse ridges which are effective to agitate and mix the material passing through the chamber. The entrance and exit openings of the chamber are constructed in the form of traps which are filled by the pulverulent material flowing therethrough, whereby the material itself acts as a seal preventing escape of gas from the chamber.

The vibration of the trough shaped conveyor overcomes to a large degree the friction between the dry particles and thereby sufficiently fluidizes the dry finely divided material that it flows through the inlet gravity trap along the floor or" the treating chamber and out the gravity outlet trap somewhat in the manner of a liquid. At the same time, the vibration loosens up the material to access by the gas and thereby improves the speed and uniformity of the reaction.

Now, in order to acquaint those skilled in the art with the manner of constructing and operating one form of my invention, I will describe an embodiment thereof in connection with the accompanying drawing, which is somewhat diagrammatic in character, it being understood that the construction depicted therein is not intended to be limiting but merely illustrative of the invention dened in the appended claims.

In the drawing:

FIGURE 1 is an elevational view, partly in section, of a preferred embodiment of the apparatus of the invention;

FIGURE 2 is a cross-sectional view taken on a line 2--2 of FGURE l; and

FGURT. 3 is a cross-sectional view taken on the line 3 3 of FIGURE 1.

Referring now to the drawing, my apparatus consists of a trough-like conveyor it), preferably having a flat, somewhat horizontal bottom wall il, having an upper reaction surface lita, and being formed with substantially vertical iianges or sides l2 to provide lateral restraint and to retain the material to be treated on the conveyor. The conveyor l@ is xed to a carrier or support member 13 by any conventional means, as by a bracket ld at one end and by welding the conveyor to the carrier at other contiguous points, as at i6 and 17. The carrier is itself adapted to conduct material discharged from the conveyor lh and, therefore, is conveniently fabricated in the form of a channel, as best shown in FGURE 2. The bottom of the conveyor, during operation, is covered with a relatively thin layer of material M to be reacted, as will appear more fully hereinafter.

Oscillatory motion is imparted to the conveyor 1t) by means of a drive unit consisting of a connecting rod i3 actuated by an eccentric it mounted in suitable bearings (not shown). The other end of the connecting rod is connected to the adjacent end of the carrier i3 by means of a pivot-bearing 2i. The eccentric 19 is driven by a pulley 22 which in turn is driven by a pulley 23 by means of a belt 24. The pulley 23 is mounted on the shaft of an electric motor 26. Pulleys 22, 23 are preferably individually adjustable as to their workin g diameters so that the speed of rotation of the eccentric 19 may be varied within desired limits. Mixing elements 27, here shown as transverse protuberances of generally triangular crosssection, are mounted on or at the bottom wall 11 of the conveyor above or as a part of the reaction surface 11a to promote plowing up or mixing of the finely divided material undergoing treatment, in accordance with the invention.

The carrier 13 is supported preferably horizontally on any suitable parallel motion mounting means which, in the form illustrated, includes flexible reaction legs or struts 2S mounted rigidly at top and bottom by brackets 29, 30, positioning the struts at the required angle to give the desired motion to the conveyor when the struts 23 are lexed by the oscillatory drive mechanism. The brackets Z9 are secured to the carrier 13, and the brackets 30 are secured to a foundation or base 31. With the construction just described, the direction of vibration imparted to the conveyor is as indicated by the double arrow 25 in FIGURE 1.

When treating a finely divided solid material with a gas it is advantageous in most instances to bring about a mixing of the solids so that all of the particles are at least eriodically in contact with the treating gas, and in the present invention this is achieved by the proper design of the mixing elements 27, by their arrangement along the bottom wall or floor of the conveyor, by the angularity of the support legs or struts 2S, and by the amplitude and frequency of oscillation of the conveyor. For the treatment of starch with hydrogen chloride gas, when the starch bed is about 1/2 thick, the mixing elements Z7 may be placed between about 3 and about 4 inches apart, as measured between corresponding points on adjacent mixing elements, and may have a height of about a width of the base, as viewed in cross-section in FIGURE 1, of about l", an acclivity or entrance angle (facing upstream relative to the direction of llow of the starch) of about a declivity or downstream angle of about 35, and an angle at the apex of about 130. Operable values for the other factors are: angularity of struts 28 about 60 to the horizontal; frequency of oscillation of the eccentric, about 400-800 cycles per minute; amplitude of horizontal motion of conveyor between about 1/s and about 1/2".

Operation of the apparatus, in accordance with the factors defined immediately above results in transportation of a finely divided material, such as starch, from right to left as viewed in FIGURE 1, during which the starch is levitated and continuously mixed, bringing the starch particles into the desired reaction contact with the hydrogen chloride gas. it is to be understood that the values of the various factors just discussed are merely illustrative, and not limiting, and that they may be varied as required for various pulverulent materials under different circumstances. For a further description of vibratory conveyors of the type just described, and the influences of the various factors on their operation, reference may be had to my copending application, Serial No. 762,464, filed jointly with Adolph Paul Oleson, on September 22, 1958.

Referring again to the drawing, it will be seen that the conveyor is provided over a portion of its length with a chamber or tunnel 32 formed by a top wall 33, which is supported by the sides 12 of the conveyor trough, and by end walls 34 depending from the top wall 33 and also extendnig completely across the conveyor trough. The top wall 33 and end walls 34 are welded or otherwise sealed to the side walls 12 of the conveyor.

The conveyor floor 11 adjacent the ends of the chamber is formed with substantially V-shaped transverse depressions 35, 35 and the end walls 34, 34 of the chamber extend respectively downwardly into said depressions, terminating above the floor of the conveyor, thereby forming an inlet 36 and an outlet 37 to said chamber.

As noted above, the starch is levitated as well as translated on the conveyor and, therefore, a substantial amount of dust would result as the levitated starch came in contact with the vertical end walls 34, 34 since the end walls have a greater horizontal velocity than that of the levitated starch. To eliminate such dusting of the starch flowing from the openings 36 and 37, flanges 33 and 38 are provided extending angularly upwardly respectively from the bottom of said end walls 34, 34 in the direction of the material flow and substantially parallel to the corresponding inclined surfaces of the depressions 35, 35.

The angles made by the walls of the depressions 35, 35 with the horizontal may be varied over a rather wide range with satisfactory results. For example, the acclivity angles of the depressions 35, 35-i.e., the angles, relative to the horizontal, formed by the inclined surfaces forming the discharge sides of the respective depressions 35, 35- may be between about 3 and about 25, the angles near 25 being preferred since they permit the overall length of the apparatus to be correspondingly shortened. Acclivity angles of the depressions appreciably in excess of about 25 are not recommended since at such steeper angles the upper layers of the starch move at a higher rate than do the lower layers of starch under the influence of the vibration of the conveyor, resulting in non-uniform exposure of the starch to the treating gas. The highest points of the inclined surfaces forming the discharge sides of the depressions 35, 35 (i.e., the inclined surfaces downstream of the inlet 36 and outlet 37, respectively) are disposed slightly (e.g., MW) above the bottom edges of the respective end walls 343, 34.

The declivity angles of the depressions 35, 35'-i.e., the angles, relative to the horizontal, formed by the inclined surfaces forming the upstream or input sides of the respective depressions-are also not closely critical. However, very small or very large declivity angles are not recommended for practical reasons since the small angles cause undue lengthening of the upstream portion of the conveyor, and the large angles promote dusting of the conveyed starch as it tumbles into the depressions. Moderate declivity angles, i.e., between about 10 and about 50, are therefore preferred.

The dimensions of the end wall 34 are such that its bottom edge is no higher than, and preferably below, the upper surface 11a of the conveyor within the chamber 32; similarly, the bottom edge of the end wall 34 is positioned no higher than and preferably below, the horizontal stretch of the conveyor upstream from the opening 36. With this arrangement, the end walls 34, 34 and the depressions 35, 35 form traps which include the inlet opening 36 and outlet opening 37, respectively, and wherein the openings 36 and 37 are disposed entirely below the tops of the respective depressions 35, 35.

A gas diffuser 39 for supplying anhydrous hydrogen chloride or other gas is provided in the chamber 32, preferably adjacent the inlet 36, and a flexible connection 40 connects the diffuser with the gas source (not shown). A feeding mechanism for the pulverulent material to be treated is provided at the input end of the conveyor, the feed mechanism being shown in the drawing as a belt 41 carried at its discharge end by a roller 42.

My apparatus and process will now be described as applied to the continuous acidification of starch. The eccentric 19 being adjusted to give an amplitude of horizontal motion of between 1A and 1/2, and the pulleys 22, 23 being adjusted to cause the eccentric to oscillate at between about 400 and about 800 cycles per minute, the motor 26 is energized and the resulting oscillations are transmitted to the carrier 13, and thence to the conveyor 10. The starch to be treated is applied continuously and at a constant rate by a gravimetric feeding mechanism (not shown) to the belt 41 which delivers the starch to the input end of the conveyor 1t). The starch is fed to the conveyor at a rate to produce a bed or stream of predetermined depth, c g., one-half inch, across the Width of the conveyor. Under the influence of the oscillatory motion of the conveyor, the starch distributes itself uniformly across the conveyor and moves as a bed through the gas treating tunnel or chamber 32 where it is contacted by anhydrous hydrogen chloride gas supplied through the gas diffuser 39. The hydrogen chloride gas is introduced into the treating chamber at a predetermined rate related to the volume of starch in the bed and to the desired degree of treatment intended for the starch.

Since the present apparatus is designed for continuous operation the inlet 36 and outlet 37 are preferably designed to have substantially the same cross-section as the cross-section of the bed of starch on the conveyor. As the starch flows longitudinally of the conveyor it fills the depressions 35, 35 in which the inlet 36 and outlet 37 are situated, thereby maintaining the inlet and outlet con stantly totally submerged in the starch bed. As has been noted, the inlet 36 and outlet 37 are disposed entirely below the tops of the depressions 35, 35 located adjacent the respective end walls 34, 34', so that the stream of starch first ows downwardly to the inlet 36, then upwardly from the inlet into the reaction zone in the chamber 32. After traversing most of the reaction zone, the starch stream flows downwardly to the outlet 37, then upwardly from the outlet exteriorly of the chamber 32. By following the vertically reversing paths required by this construction, the starch continuously fills the inlet 36 and outlet 37, and thus the starch itself acts as the means for sealing the reaction chamber to prevent the escape of hydrogen chloride gas. Moreover, with the construction just described it will be appreciated that the openings 36 and 37 will remain submerged in the starch being treated even though the starch is fed to the conveyor at a rate which is not constant, and even if the starch input to the conveyor is interrupted altogether. Under the influence of the mixing elements 27 the starch passing through the chamber is thoroughly plowed or mixed, thereby vastly increasing the exposure of the starch particles to the hydrogen chloride gas for reaction therewith.

It will, of course, be understood that an important feature of my invention, i.e., the provision of vertically reversing paths for the particulate material providing sealing traps at the ends of the reaction zone, may be practiced whether or not any means is provided for miX- ing the solid particles in the reaction zone. It will also be obvious that those skilled in the art may make various changes in the details and arrangement of parts in my apparatus without departing from the spirit and scope of the invention as defined in the appended claims, and it is therefore not intended that the invention should be restricted to the precise construction herein disclosed.

l claim:

l. In a method of contacting dry finely divided particles with a gas wherein a stream of said dry particles is conducted continuously through a confined contact space containing said gas and having an inlet and an outlet, the improvement which comprises causing said stream to en* ter said contact space by flowing through a vertically reversing path which includes said inlet, causing said stream to leave said contact space by flowing through a vertically reversing path which includes said outlet, and maintaining the flow of said stream sufficiently high that said inlet and outlet are continuously filled with said dry particles so that the flowing particles themselves effectively inhibit the egress of gas through said inlet and outlet from the chamber.

2. A method of contacting dry finely divided particles with a gas which comprises conducting a stream of Said dry particles continuously through a confined contact space space containing said gas and having an inlet and an outlet, causing said stream of dry particles to enter said confined space by flowing downwardly to said inlet and upwardly away from said inlet into the said space, causing said stream of dry particles within said space to flow downwardly to said outlet and upwardly away from said 6 outlet exteriorly of said space, and maintaining the flow of said stream of dry particles at a sufficiently high level such that the said inlet and outlet are continuously submerged therein and so that the flowing particles themselves effectively inhibit the egress of gas through said inlet and outlet from the chamber.

3. In a method of modifying starch wherein a stream of dry finely divided starch is conducted continuously through a confined reaction zone having an inlet and an outlet, the improvement which comprises causing said stream 0f dry starch to enter said reaction zone by flowing through a vertically reversing path which includes said inlet, causing said stream to leave said reaction zone by flowing through a vertically reversing path which includes said outlet, maintaining the flow of said stream of dry starch at a high level such that said inlet and outlet are continuously filled with dry starch, and introducing hydrogen chloride gas into said reaction zone other than through said inlet and outlet at a predetermined rate related to the volume of said stream of starch, the flowing particles in the inlet and outlet effectively inhibiting the egress of said hydrogen chloride gas therethrough from the chamber.

4. A method of modifying starch comprising conducting a stream of dry finely divided starch continuously through a confined reaction zone having an inlet and an outlet, causing said stream to enter said Zone by flowing downwardly to said inlet and upwardly away from said inlet into said reaction zone, agitating and mixing the dry particles of said stream within said zone, causing said stream within said zone to flow downwardly to said outlet and upwardly away from said outlet exteriorly of said zone, maintaining the flow of said stream of dry starch at a height such that said inlet and outlet are continuously submerged therein, and introducing hydrogen chloride gas into said reaction zone other than through said inlet and outlet at a predetermined rate related to the volume of said Stream of starch, the fiowing particles in the inlet and outlet themselves effectively inhibiting the egress of said hydrogen chloride gas therethrough from the chamber.

5. A method of contacting dry finely divided starch particles with a gas which comprises feeding the dry starch particles onto one end of a conveyor surface, oscillating said conveyor surface sufficiently to move a stream of the dry particles across said surface and through the inlet of an enclosed contact area intermdiately disposed on said surface and Containing gas, there to mix the dry particles of the stream with the gas and afterwards to exit the stream from said area through its outlet to the opposite end of the conveyor surface, collecting the gascontacted dry starch particles at said opposite end, and maintaining the level of the particles suiiiciently high with respect to the inlet and outlet of said enclosed area that said inlet and outlet remain continuously submerged in the stream of dry starch particles so that the inleting and exiting particles themselves inhibit the egress of gas from the contact area.

6. A method of contacting dry finely divided particles with a gas which comprises feeding the dry particles onto one end of a surface having an enclosed contact space with an inlet and an outlet not higher than the immediately adjacent portions of said surface on each side of said inlet and outlet, adding gas to said space, and oscillating the surface sufficiently to move a stream of the dry particles downwardly to the inlet and upwardly into the space for contact by the gas, then downwardly to the outlet and upwardly and away from said outlet to the other end of said surface, there collecting the gas-contacted particles, while maintaining the level of the particles as they pass through the inlet and outlet sufficiently high that the inlet and outlet submerged in the stream of dry particles and the egress of gas is inhibited therethrough by the passing particles themselves.

7. The method of moving a dry finely divided material through a gas containing chamber having downwardly dipping inlet and outlet passages at the junction of each end wall and the bottom wall which comprises forming the dry material into a thin uidized stream by mechanical vibration and passing the uidized stream through 5 said passages and along the bottom wall of the chamber while maintaining the level of said dry material Suciently high at the inlet and outlet that the material itself seals the chamber at said passages to inhibit the egress of gas therethrough from the chamber. 10

References Cited in the file of this patent UNITED STATES PATENTS Browning et al. Oct. 25, 1904 8 Jeffries Oct. 3, Fuller Jan. 9, Englemann et al June 27, Burns Feb. 25, Green Sept. 4, Green June 19, Marshall Dec. 25, Sylvest Apr. 13, Spooner Nov. 29, Blau Feb. 28, Irish Nov. 8, Kayatz Nov. 28,

FOREIGN PATENTS Switzerland Dec. 23,

r l V i I UNITED STATES PATENT rOFFICE CERTIFICATE OF CORRECTION Patent Nm 3V114656 ,December-'1m 1963 Robert L Ople It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2v line 67 for "18" read -e 19 columnI 6v line l?! before "dry" insert 4said Signed and sealed this 5th day of May 1964.-a

(SEAL) Attest:

ERNEST Wc SWIDER Attesting Officer EDWARD J., BRENNER Commissioner of Patents 

1. IN A METHOD OF CONTACTINGDRY FINELY DIVIDED PARTICLES WITH A GAS WHEREIN A STGREAM OF SAID DRY PARTICLES IS CONDUCTED CONTINUOUSLY THROUGH A CONFINED CONTACT SPACE CONTAINING SAID GAS AND HAVING AN INLET AND AN OUTLET, THE IMPROVEMENT WHICH COMPRISES CAUSING SAID STREAM TO ENTER SAID CONTACT SPACE BY FLOWING THROUGH A VERTICALLY REVERSING PATH WHICH INCLUDES SAID INLET, CAUSING SAID STREAM TO LEAVE SAID CONTGACT SPACE BY FLOWING THROUGH A VERTICALLY REVERSING PATH WHICH INCLUDES SAID OUTLET, AND MAINTAINING THE FLOW OF SAID STREAM SUFFICIENTLY HIGH THAT SAID INLET AND OUTLET ARE CONTINUOUSLY FILLED WITH SAID DRY PARTICLES SO THAT THE FLOWING PARTICLES THEMSELVES EFFECTIVELY INHIBIT THE EGRESS OF GAS THROUGH SAID INLET AND OUTLET FROM THE CHAMBER. 